The effect of aldosterone on the amiloride-sensitive sodium transporter from epithelial tissue will be studied. This transporter has been identified and characterized in a particulate fraction. This transporter will be purified with the aid of a lipid reconstitution assay currently being developed. A microsomal fraction from epithelial tissue will be added to a mixture of purified lipid and detergent and the detergent dialyzed away. The uptake of 22Na ion into the reconstituted vesicles will be determined with special attention paid to amiloride-sensitivity. Next detergent-extracts of the tissue will be separated into different protein fractions by a variety of protein-purification procedures and the purified protein fractions reconstituted into vesicles. Using the reconstitution assay to the amiloride-sensitive Na ion carrier will be purified and the ability of aldosterone to stimulate its synthesis determined.